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Deep trench marine life filmed

The marine life of a previously unexplored deep ocean trench has been captured on camera for the first time.

Scientists studying the New Hebrides Trench in the South Pacific used remotely-operated equipment to film the swarms of large bright red prawns and cusk eels that dominate the area.

But the biologists, from the University of Aberdeen and a research institute in New Zealand, said they were surprised at the lack of diversity in the marine life inhabiting the 4.5-mile deep trench.

Its location in tropical waters east of the isle of New Caledonia could help explain the contrast with the biodiversity found in other deep trenches in the Pacific Rim, they said.

The expedition was the 11th undertaken by Dr Alan Jamieson, from the University of Aberdeen's Oceanlab, to the area.

He said: "Fish were surprisingly few in number and low in diversity and not at all what we expected. The fish we would always expect to see, the grenadiers, were completely absent. The fish that dominated the area were a group called cusk eels which are far less conspicuous elsewhere.

"As well as the difference in biodiversity we also stumbled across another surprise - the area in and around the New Hebrides Trench was swarming with large bright red prawns which are typically seen in very low numbers in other areas."

Fellow Oceanlab marine biologist Thom Linley said: "The big difference between this trench and others that we have studied is that the New Hebrides Trench lies underneath tropical, and therefore less productive, waters.

"The waters over a trench are what 'feeds' the deep sea community and in this case it appears that the prawns and cusk eels are specialists in low food environments.

"This means the huge expanses of the deep Pacific Ocean that span the tropical regions are likely to be largely inhabited by the cusk eels and prawns rather than the more diverse communities we see around the Pacific Rim. If that is the case it also means that these animals are far more widespread than previously thought."

Dr Jamieson said the findings highlight the potential impact of climate change on life in the deepest parts of the ocean.

He said: "These new finds are a stark reminder that even the deepest parts of the world are intrinsically linked to the productivity of the surface waters.

"Should the current system change, it is highly likely to have significant cascading effects on the deep sea community. The deep sea is potentially a kind of silent victim in the era of a changing climate."

The expedition, carried out with the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, obtained rare samples of cusk eels and crustaceans as well as camera footage and images.

It was the last voyage of a seven-year series of projects titled The Hadal Environmental and Education Partnership (Hadeep).

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